00:01
So in this problem, archer has 0 .6 accuracy.
00:04
And after she takes a new lesson, she has 0 .625 new accuracy.
00:08
So she's able to hit five in the target in five out of eight attempts.
00:16
And in part a, we're going to find the probability that she would have hit five out of eight before her lessons, when the new coach, before this new accuracy.
00:26
So at least five out of eight.
00:32
Means we're going to add the probability of her hitting 5, 6, 7, and 8, exactly.
00:39
So the probability of hitting 5 is 0 .6, the 5th, times 0 .4, which is the failure.
00:49
So failure rate to the third power times 8 factorial divided by 5 factorial times 3 factorial, because there's going to be different combinations where different possibilities where five targets are hits out of the total eight.
01:07
And we're going to add that with, i'm going to add this with the probability of her hitting exactly one, or exactly six, sorry, exactly six, which is 0 .6 to the six power times 0 .4 to the second power, times 8 factorial divided by and change these exponents into factorials...